Reactive pasty two- or multi-component systems must be stored separately after their production and until their application in order to prevent premature, inadvertent reactions of the components. Cartridge system for the application of pasty two- or multi-component systems have been known for decades. The following documents are cited for exemplary purposes, CH 669 164 A5, EP 0 607 102 A1, EP 0 236 129 A2, DE 3 440 893 A1, U.S. Pat. No. 4,690,306 A, US 2009/062808 A1, EP 0 787 535 A1, WO 2006/005 206 A1, EP 0 693 437 A1, EP 0 294 672 A, EP 0 261 466 A1, and EP 2 008 707 A1. The pasty two- or multi-component systems are mixed right before their application, usually through the use of static mixers. The following documents are cited for exemplary purposes, GB 1,188,516 A, U.S. Pat. Nos. 2,125,245 A, 5,968,018 A, 4,068,830 A, US 2003/179648 A1, EP 0 664 153 A1, and EP 0 289 882 A1. After the cartridges are filled with reactive pastes, the cartridges need to remain closed until their application. In this context, mobile plungers, which are also used to dispense the cartridge content, usually seal the cartridge floors.
A number of solutions has been proposed for closing the cartridge system head of the cartridge system.
One simple, but very effective, principle is to close the cartridge head with a closure that can be rotated (EP 0 431 347 A1, DE 2 017 292 A1, U.S. Pat. No. 3,215,298 A). The closure is unscrewed prior to the application. Subsequently, a dispensing tube is screwed into a thread on the cartridge head or fixed through a peg system that simulates a thread. This is disadvantageous in that the user needs to perform rotational motions twice until the paste material can be expelled. Moreover, the closure may be screwed out and the dispensing tube is attached only later. In the interim between the cartridges being opened and the dispensing tube being inserted, ingredients of the pastes may evaporate, especially if the pastes contain volatile substances.
The closure that is in very common use currently in the adhesives and sealant industry is based on the wall material of the cartridge being provided to be very thin at the cartridge head such that said wall can be perforated easily. During perforation, particles may become detached from the wall and can thus enter the pasty material.
The backside of the cartridges is usually closed by mobile plungers that are designed for expelling the pastes during application. In the case of humidity- and air-sensitive pastes, aluminium cartridges may be used that are closed by plastic plungers and over which aluminium cylinders that are closed on one side are pressed in for sealing purposes. During the application of the pastes, the aluminium cylinder having one closed side is moved jointly with the plunger towards the front in the direction of the cartridge head through the action of cartridge applicator guns and the paste is expelled in the process. However, any contact of paste and aluminium surfaces may be problematic in medical applications.
Using cartridge systems for sterile pasty medical products, there is a need for not only the pastes, but obviously the cartridges and secondary packaging means also to be provided in sterile form to the user. For example after aseptic filling of the previously sterilised cartridges, these may be transferred directly to sterile packaging means. Moreover, it may make sense for certain products to sterilise the surfaces of filled cartridges jointly with the packaging means after packaging is completed. Aside from gamma sterilisation, which cannot be used with paste systems that can be polymerised, there is the option to use ethylene oxide gas for sterilisation.
However, one issue of said sterilisation with gas in the case of paste systems containing monomers with a high vapour pressure is that a fraction of the monomers in the cartridges evaporates after the actual sterilisation, when the residual ethylene oxide is removed by the action of a vacuum, whereby the monomers form a gas phase in the cartridges and can thus exert a pressure against the plungers. This means that the plungers are moved in the direction of the cartridge floors in undesired manner and may be expelled from the cartridges in the extreme case such that the pastes may leak out.
Polymethylmethacrylate bone cements have been in use in medicine for decades for permanent mechanical fixation of total joint endoprostheses. They are based on powder-liquid systems. Recently, polymethylmethacrylate bone cements that are based on the use of cement pastes have been proposed also (DE 10 2007 050 762 A1, DE 10 2008 030 312 A1, DE 10 2007 052 116 A1). Thus far, no suitable cartridge systems have been proposed for said cements.
With regard to the application of bone cements for fixation of total joint endoprostheses, it is always necessary to take into consideration that the OR staff is under time pressure during these surgeries. Therefore, as a matter of principle, cartridge systems for medical applications involving the application of paste-like polymethylmethacrylate bone cements should be designed such that they are largely resistant to user errors and can be operated rapidly and safely even in stressful situations.
The methylmethacrylate monomer is an essential ingredient of paste-like polymethylmethacrylate bone cements. Said monomer evaporates readily and has a relatively high vapour pressure at room temperature. For this reason, it is essential to note with regard to the use of methylmethacrylate-containing pastes that the cartridge plungers in the cartridges may be moved and may be expelled from the cartridges in the extreme case by the evaporating methylmethacrylate upon exposure to vacuum, such as during the de-gassing as part of ethylene oxide sterilisation. A cartridge system of the kind is based on packaging pasty multi-component systems in tubular bags (WO 2010/006455 A1). In this context, the sealed tubular bags are inserted into cartridges. Tubular bags are advantageous in that they are suitable for packaging pastes that contain volatile ingredients. Tubular bags made of compound materials, such as aluminium compound bags, are particularly well-suited. The tubular bags are opened by blades that rotate along when the dispensing tube is screwed in. During the rotational motion of the blades, the bags are cut open, and openings in the cartridges for dispensing the content are thus provided. The pasty bag content is subsequently squeezed through these openings in the cartridges in the direction of the static mixer.
In this context, it is disadvantageous that packaging pasty materials in tubular bags and, in additional, in cartridges is quite expensive and reserved for special applications only. Moreover, it is a problem in many applications, especially in the field of medicine, that parts of the cut tubular bags may become detached and thus may enter into the pasty components and thus contaminate the mixing ware.